Gland packing



Aug. 26, 1947. P, E, LY'DDON l 2,426,461

' 'GLAND PACKING Filed oaku 51, 1944 s sheetsfsheet'l ug.{ 26, 1947. l P, E, LYDDON 2,426,461

GLAND PACKING Filed Oct. 31, 1944 3 Sheets-Sheet 2 Aug. 26, 1947. P. E. LYDDON 2,426,461

GLAND PACKING l Filed dov. 31, 1944 5 Sheets-Sheet' n Patented Aug. 26, 1947 GLAND PACKING :Percy jEdwardLyddon, Worcester, England, as-

signor to Morgan Crucible Company, Limited,

London, YEngland Application october 31, 1944, serial No. 561.214 I-n Great Britain November 1,` Y1943 Claims.

This invention 'relates toV improvements in gland packings between relatively vrotating coaxial parts lsuch 'as a Jsh'aft rotating in a housing, for preventing leakage of a vfluid medium under pressure from 'one 'compartment to an adjoining one of lowerpres'su're or to the atmosphere. l

The Vinvention Vparticularly concerns an improvement as Vcompared with normal labyrinth glands em'ployin'g'fi'ns ori like throttling `projections wh'ich rub against or are disposed 'in close relationship with f anopposing surface so as to prevent steam from leaking vout of the casing of 'a turbine 'at the lpoint of entryfof the .shaft or between successive stages vof 'the turbine withinV the cylinder. y Y

In previous practice such labyrinth glands .have suffered from `the disadvantage that although various steps may be taken to .keep 'it as small as possible an vappreciable clearance may exist between the edges of the fins and the opposing surface; and this clearance may become so large as to permit a considerable leakage of steam,

It is well known that the volume of steam escaping through aclearance between opposed ksurfaces increases very considerably with any increase in the said clearance, and itis the object of the present .invention to Amake this clearance as small as possible .andto prevent it from increasing as, 'for example, by any wear such as is caused in usual designs .by small displacements of the axis of rotation Aof the shaft `relative to the housing or stator around it.

According to the invention a Vpacking between relatively rotating yco-axial parts comprises 'a member rotatable with, but axially displaceable with respect to, one part and having a surface Ain throttling sealing relationship with a -corresponding'surfacefofsaid part and a member carried by the other part, or the other part itself,

or metallic bearing material, mounted in the housing and presenti-ng a side face into AContact With 4an -end surface ofthe collar. Alternatively, if the Amaterial "of :the housing Sis suitable, ia

lside face of the housing ritself may be presented into contact with the collar.

The inner surface of the collar is not necessarily in labyrinth-sealing relationship with the shaft but may oppose a smoothsurface to vthe shaft, throttling being achieved by 4providing a very small Aclearance between the'collar land the l shaft.

A limit may be imposed on the axial displacement "of thejaxially Adispla'cea'ble vmemberso that after ascertain extent of wear at the surfaces which bear against each other in the axal'direction no further axial displacement is permitted.

In addition to the sealing surfaces facing the axial direction, the respective relatively `rotating parts or memberscarr'ied thereby, may also have surfaces extending 'in the axial direction which are in sealing relationship, and a 'labyrintheifec't may be produced between theseA surfaces by, providing fins orlike `throttling 'projections on one or both of them.

According to an embodiment 'of 'the invention applied to the shaft of va turbine, va vcollar is mounted on the shaft so as to be rotated thereby but to be free to ioat axially thereon. The lcollar may be in one piece or split in half to 'facilitate assembly. A 'labyrinth is formed Aby providing a number of grooves in the inner cylindrical surface of the collar where it opposes the outer cylindrical surface of the shaft. As there is no relative movement between the shaft and the collar it drives the clearance `between them can fbe made very small without appreciable risk. Since the labyrinth sealing surface must participate with any movement of the shaftthe vclearance remains unaffected by any displacement of the axis of rotation of the shaft and 'remains `constant throughout the life 'of the turbine.

ing collar and the latter is forced axially'by'the pressureof the steam against the side of the ring and thus forms a sealing surface with it. The rotation of the collar may be ensured by any of the various known means such as by a vfeather lor sliding Akey or by lugs projecting from a shoulder on the shaft into recesses formed in thecollar. Ior .by a screw -xed -in the shaft-and working ina slotted recess in the collar.

In A'order Ito ensure that no rusting shall occur between 'the bore of 'the collar and the opposited by providing a stop secured to or formed on the shaft and projecting above the surface of the shaft, so located that after the bearing material has worn and the collar is moved axially by any desired amount, the latter engages with the stop which then supports the axial thrust ofV the steam on the collar. Thereby the pressure of the collar n the bearing material is'relieved and no further wear by rubbing can take place. y

Nevertheless the seal between the collar and the bearing material remains effective since at the time the pressure between them is relieved, the opposing surfaces are in the closest possible proximity to one another.

The radial surface of the collar where it o-pposes the side surface of the bearing material may be mounted with concentric grooves forming a labyrinth in the manner described in my copending application Serial No. 568,855, filed December 19, 1944. In this case a smaller limit is preferably imposed on the axial movement of the collar.

The ring of bearing material may consist of a single piece ring or of a ring made up of a number of segments. n

In some cases instead of the collar having a radial surface in sealing relationship with a side surface of the bearing material, these surfaces may be inclined so as to have a radial component as well as an axial component.

The invention is illustrated by way of example in the accompanying drawingsin which Figure 1 is a sectional elevation of one form of the gland packing.

Figure 2 is a section on the line 2 2 of Fign ure 1;

Figures 3, 4 and 5 are part sectional elevations of three modifications of the packing; and

Figure 6 is a part sectional elevation showing the gland packing used in conjunction with a carbon sealing ring.

In the drawings i indicates a shaft rotating in a housing 2. On the shaft i is mounted a collar 3 so as to be capable of axial movement along the shaft but rotatable therewith by reason of the studs 4 carried by the .shaft engaging in recesses 5 in the collar.

The end face 6 of the collar bears on the side face of a carbon gland ring 3 mounted in a recess in the housing 2.

An abutment 9 limits the axial displacement of the collar so that after a certain extent-of wear of the gland ring S no further axial displacement is permitted.

In Figures 3 and 5, the inner peripheral surface of the collar is grooved to provide fins i3 and hence a labyrinth-sealing relationship with the shaft. v

In Figures l, 2, 3, 4 and 5 axial holes i4 are provided in the enlarged end of the collar to equalise the pressure on both sides thereof.

In Figure 6, which is more diagrammatic and where the arrangement is reversed in that the higher fluid pressure is considered to be on the left hand side, a segmental carbon sealing ring the closest possible proximity.

4 l5 surrounded by a garter spring IB and bearing on the shaft and against the inside of the end wall of the casing, all in known manner, serves to make a nal seal, for example to atmosphere.

In comparing the clearance usually allowed with labyrinth glands it will be evident that the clearance between the collar and the shaft and for a kcorresponding axial length is. such that the leakage with the packing of the present invention may be approximately 1% of that of the former; furthermore this clearance remains constant in the Working of the turbine. The clearance between the outer axial surface of the collar and the housing may be comparatively great, as no leakage would normally occur there, and no radial Yforce need therefore ever be exerted on the shaft.

Reference to Figures l, 2 and 3 shows the collar 3 made in two halves secured together by bolts l0. In these figures, also, pressure of springs il is applied to the collar to urge its end face 6 against the gland ring 8. This pressure augments that'due to the higher fluid pressure on the righthand side of the packing which, per square inch, is a function of the ratio of the area of the right hand end face of the collar to the area of the end face 6 which is in contact with the gland ring 8, which ratio can accordingly be designed to suit requirements. In Figures 4 and 5, representing an example where the iiuid pressure drop from the right to the left of the packing is high, spring pressure is not applied and the pressure per square inch on the gland ring 3 is reduced as compared with the pressure on the right hand end face of the collar.

In each of Figures 1, 3, 4 and 5 the outer peripheral surface of the collar, extending in the axial direction adjacent to a cornering surface of the housing, is in labyrinth-sealing relationship with the housing vby the provision of the collar with fins I2.

VIn the course of time when wear has taken place to the lextent that the collar reaches the stop no bearing pressure is then exerted at the seal between the end face of the lcollar and the gland ringy 8l although thereafter they remain in The aforesaid labyrinth therefore limits the leakage possible even through this-extremely close gap after the described condition has been reached.

The labyrinth may have any of the usual forms and the opposing surface may be of carbon or the like so asto ensure the minimum clearance.

Whatl claim is:

l. A packing between a shaft and a surround- `1in`g housing comprising'a collar keyed'to the shaft so as te rotate therewith but to be axially displaceable thereon, the inner surface of the collar being in throttling sealing relationship with the shaft, and the outer surface of the collar having grooves to produce aV labyrinth-sealing relationship with the surrounding housing, and the housing presenting `a surface into contact in the axial direction with a surface of the collar extending away from kthe shaft, and mutually engaging means on the collar and the shaft respectively serving to impose a limit on the said axial displacement so that after a certain extent of wear at the surfaces which bear" against each other in the axial direction no further axial displacement is permitted. t

2. A packing between a shaft and a surrounding housing comprising a'collar keyed to the shaft so as to rotate therewith but to be axially displaceable thereon, the inner surface -of the collar being in throttling sealingrelationship with the shaft, and the outer surface of the collar having grooves to produce a labyrinth-sealing relationship with the surrounding housing, a, gland of a suitable bearing material embodied in the housing and presenting a side face into contact in the axial direction with a surface of the collar extending away from the shaft, and mutually engaging means on the collar and the shaft respectively serving to impose a limit on the said axial displacement so that after a certain extent of Wear at the surfaces which bear against each other in the axial direction no further axial displacement is permitted.

3. A packing as claimed in claim 2 including a spring for applying pressure to the collar to urge it towards the surface against which it bears in the axial direction.

PERCY EDWARD LYDDON.

REFERENCES CITED `The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,249,188 Stevenson July 15, 1941 1,006,714 Bell Oct. 24, 1911 1,880,911 Durdin Oct. 4, 1932 FOREIGN PATENTS Number Country Date 157,116 Switzerland 1932 414,835 Great Britain 1934 

